Methods of forming a film are well known. An early disclosure is in U.S. Pat. No. 3,218,776. In that method the film is thermoformed into pouches and filled while travelling in a circular path. One disadvantage with present systems is that it is difficult to operate them at production speeds as high as would be desirable while maintaining product quality. Another problem is that it is desirable, for cost and functional reasons, to use a film which is as thin as possible but decreasing the thickness of the film increases the risk that the film will be undesirably weakened, and possibly even perforated, at some points in the final product, especially during high speed, high under-pressure, production conditions. Another problem is that it is necessary to apply a large vacuum (high under-pressure) and it can be difficult to provide such a pressure efficiently in the moulds in a manner which does not interfere with the overall operation of the process.
The object behind the invention is to solve these problems individually and, preferably, in combination.